It has been known that, in organisms such as typically mammals, histamine which is a physiologically-active endogenous factor functions as a neurotransmitter and has extensive pharmacological activities (for example, see Life Science, Vol. 17, p. 503 (1975)).
Immunohistochemical studies have made it clear that a histamine-agonistic (producing) cell body exists in the nodal papillary nucleus in a posterior hypothalamic region and that histamine nerve fibers project in an extremely broad range in the brain, which supports various pharmacological effects of histamine (for example, see Journal of Comparative Neurology, Vol. 273, p. 283). The existence of histamine-agonistic nerves in the nodal papillary nucleus in a posterior hypothalamic region suggests that histamine may have an important role in control of physiological functions relating to brain functions, especially to hypothalamic functions (sleep, vigilance rhythm, incretion, eating and drinking action, sexual action, etc.) (for example, see Progress in Neurobiology, Vol. 63, p. 637 (2001)).
The existence of projection to the brain region that relates to vigilance sustenance, for example, to cerebral cortex suggests the role in control of vigilance or vigilance-sleep cycle. The existence of projection to many peripheral structures such as hippocampus and amygdaloid complex suggests the role in control of autonomic nerves, emotion, control of motivated action and learning/memory process.
When released from producing cells, histamine acts with a specific polymer that is referred to as a receptor on the surface of a cell membrane or inside a target cell, therefore exhibiting its pharmacological effects for control of various body functions. Heretofore, four types of histamine receptors have been found. In particular, the presence of a histamine receptor that participates in the central and peripheral nervous functions, histamine-H3 receptor, has been shown by various pharmacological and physiological studies (for example, see Trends in Pharmacological Science, Vol. 8, p. 24 (1987)); and recently, human and rodent histamine-H3 receptor genes have been identified and their existence has been made clear (for example, see Molecular Pharmacology, Vol. 55, p. 1101 (1999)).
It is suggested that histamine-H3 receptor exists in the presynaptic membrane of central or peripheral neurocytes and functions as a self-receptor, therefore controlling the release of histamine and controlling the release of other neurotransmitters. Specifically, it is reported that a histamine-H3 receptor agonist, or its antagonist or inverse-agonist controls the release of histamine, noradrenaline, serotonin, acetylcholine or dopamine from nerve ending. For example, the release of these neurotransmitters is inhibited by an agonist such as (R)-(α)-methylhistamine, and is promoted by an antagonist or inverse-agonist such as thioperamide (for example, see Trends in Pharmacological Science, Vol. 19, p. 177 (1998)).
WO99/22735 disclose the compounds similar to this invention. The compounds disclosed in this publication have a carbonyl group corresponding to R substituent in the present invention, however the compound of the present invention doesn't have a carbonyl group in R substituent. So this publication is different from the present invention. Furthermore the usage of the reference is different from that of the present invention, because the invention of the reference is related to Somatostatin agonist.